1. Field of the Invention
The present invention relates to a thin film magnetic head mounted with a magnetic transducer element and a method of forming the same, and a head gimbal assembly mounted with the thin film magnetic head, head arm assembly, and magnetic disk device.
2. Related Art
A magnetic disk device has been used for write and read of magnetic information (hereinafter, simply mentioned as information). For example, the magnetic disk device includes a magnetic disk for storing information, and a thin film magnetic head for writing information into the magnetic disk and reading information written in the magnetic disk. The magnetic disk is supported by a spindle of a spindle motor fixed to a housing, and rotated with the spindle as a center. On the other hand, the thin film magnetic head is formed on one side face of a magnetic head slider provided on one end of a suspension, and includes a magnetic write element having an air bearing surface (ABS; Air Bearing Surface) facing a magnetic disk, and a magnetic read element. In particular, an MR element exhibiting a magnetoresistive (MR) effect is typically used for the magnetic read element. The other end of the suspension is attached to a tip of an arm rotatably supported by a fixed shaft protrusively provided on the inside of the housing.
In recent years, increase in write density (increase in capacity) of the magnetic disk is advanced, and decrease in write track width is advanced along with this. When the write track width is decreased in this way, size of a thin film magnetic head is also reduced. Therefore, the magnetic write element is reduced in signal writing ability into the magnetic disk, and intensity of a signal magnetic field from the magnetic disk is also reduced. To compensate such function reduction, for example, a further strong write magnetic field needs to be generated, or magnetic spacing needs to be decreased (ABS of the thin film magnetic head is made close to a surface of the magnetic disk).
Thus, for example, it is considered that a larger write current is flown during information writing operation in order to generate a strong write magnetic field. However, when a large current is flown, the thin film magnetic head itself is heated, which may follow expansion of the magnetic head to the magnetic disk, so-called thermal protrusion. When thermal protrusion occurs in this way, a magnetic write device possibly becomes insufficient in reliability as the device.
Many techniques for suppressing thermal protrusion have been reported. For example, Japanese Utility Model Patent Publication No. 2-101308, Japanese Unexamined Patent Publication No. 2004-22003, Japanese Unexamined Patent Publication No. 2004-362660, and Japanese Unexamined Patent Publication No. 2003-91802 disclose suppression of thermal protrusion by providing a radiation layer including metal on a magnetic layer to improve heat radiation (first measure). Moreover, for example, U.S. Pat. No. 6,989,963 discloses suppression of thermal protrusion by providing a radiation layer including a material having a large heat conductivity in a manner of covering a thin film coil for generating a magnetic flux, so that heat radiation is improved (second measure). Moreover, for example, “On the Thermal Behavior of Giant Magnetoresistance Heads” B. K. Gupta, Kenneth Young, Samerra K. Chilamakuri, Aric K. Menon, pp. 380-387, vol. 123, APRIL 2001 discloses suppression of thermal protrusion by providing a thermal expansion suppression layer including a material, which has a small thermal expansion coefficient and a large heat conductivity, directly on the magnetic layer, so that heat radiation is improved, and displacement of the magnetic layer or the like to the magnetic disk is suppressed (third measure). Moreover, for example, Japanese Unexamined Patent Publication No. 2005-285236 discloses suppression of thermal protrusion by providing a thermal expansion suppression layer as the above on a magnetic layer via a protective layer including alumina, so that the magnetic layer or the like is prevented from being displaced to the magnetic disk (fourth measure).